试论均匀状厚层灰岩水动力剖面及实际意义

HYDRODYNAMIC SECTION OF THICK HOMOGENEOUS LIMESTONE AND ITS PRACTICAL SIGNIFICANCE

在均匀状厚层灰岩水动力削面上,Ⅲ、Ⅳ水动力带由于双重介质的组合条件不同,导致其水动力带的流态与流场中一系列水动力特征上的差异,在人工抽(排)水影响下能形成“双层水位”。应用此自然规律合理设计矿山开采方案,将能从根本上避免地面塌陷。

Four hydrodynamic zones can be recognized in tbe bydrodynamic section of hugely tbick bomogeneous limestone. Tbere are lots of differences in bydrodynamic feature between hydrodynamic zone III and hydrodynamic zone IV. The water - bearing medium structure of the hydrodynamic zone III is made up of corrosive fissure - corrosive conduit whith is called large double-medium, and fissure - corrosive fissure which is called small double-medium. The former forms cave flow( turblent fast flow) and the latter forms fissure flow (laminal slow flow) in the wall rock. Transform from one form to another is complicated. The underground rivers drain off water from the wall rock and closely relate to rainfall. The hydrodynamic zone IV is made up of corrosive fissure, corrosive cave and fissure. Part of the karst water recharge is from the leakage from zone III but most of it is from the lateral recharge of deep groundwater. So the flows of this zone run slow under the hydro- pressure, it is confined water. There occurs the 'double-layer' water table of the hydrodynamic zone III and the hydrodynamic zone IV in the natural flowing condition. There is a interzone between the hydrodynamic zone III and IV in which the large double- medium water changes into small double- medium water It relatively obstructs water and causes double-layer water table. Overextraction of water from zone III may bring about great change of the hydrodynamic condition and lead to earth-subsidence in the area of Cone of drawdown depression. Deep drainage from pit in the zone IV could form Cone of drawdown depression of large area, but can't bring about the change of water table of zone III and so can't lead to the earth subsidence. This is the effect of the existing of the 'double -layer' water table. We can draw great inspiration from this natural phenomenon to change the unreasonable traditional drainage design of water source place. Water of zone III should not be overextracted and natural flowing regime of zone III should not be changed. This is the effective way to avoid the earth subsidence. The thorough research of the hydrodynamic section of huge thick homogeneous limestone is of great significance in both theory and practice.